Tucked against a wall in a hot, overstuffed room at Heritage Hall on Wednesday, an unassuming teenager wearing blue jeans and a T-shirt watched Lane Kiffin try to explain why he was the best man to take over the USC football program.

The kid with the wavy blond hair was quite literally the most important person in the room, and nobody even noticed he was there.

That’s because everyone’s attention was fixated on Kiffin, who was getting grilled by an unrelenting media throng wondering why he left Tennessee after just one year to return home to USC as Pete Carroll’s successor.

Or how he could stand there and legitimately say he intends to run a clean program, when the one he just left is still living down the seven secondary infractions he committed in just 14 months on the job.

Mostly they wondered why a 34-year old with less than three seasons of head coaching experience and a 12-21 overall record should be entrusted with one of the great jobs in all of college football.

The questions came one after the other and Kiffin defended himself as best he could.

He told them USC has been his dream job ever since he joined Carroll’s first staff as a 25-year-old assistant in 2001, then spent the next six seasons helping Carroll preside over one of the most dominant runs in college football history.

“It was a difficult decision, but it became very obvious when we had the chance to come back here, we were coming back to the greatest job in America,” Kiffin said.

Kiffin promised them his experience at Tennessee taught him about paying attention to detail when it comes to the thick NCAA rulebook, and how his No. 1 priority is running a pristine program.

“We need to have complete attention on making sure we are running this program with great discipline, and we are in compliance with all the rules,” Kiffin said. “And I don’t know if I could have done that 14 months ago, and sat here and told you I could have done it as well as I could now.”

And he was sure to point out the strong supporting cast he’s assembling, the one he can grow and learn from.

His father Monte, one of the most respected minds in all of football, will run the Trojans’ defense. Ed Orgeron, the ace recruiter and former Carroll assistant, joins Kiffin from Tennessee.

And Lane Kiffin promises even more significant additions in the near future.

“It’s going to take time, but we will put together a great staff,” he said.

Some people bought it, others weren’t so sure.

Kiffin has a lot to prove to people, and it’s going to take more than one introductory news conference for them to believe USC athletic director Mike Garrett made the right call when he tapped Kiffin as the next head coach.

Especially with the Trojans coming off a fifth-place finish in the Pacific-10 Conference, their worst in eight seasons, and with possible NCAA sanctions looming over the program.

The kid in the blue jeans couldn’t care less who is on board and who isn’t.

Matt Barkley is all in, and for Kiffin and USC, maybe that’s all that matters.

“It was pretty interesting seeing him get grilled like that, the way he handled it and all,” said Barkley, the Trojans’ quarterback. “It was to be expected, I guess. People are going to have questions, especially with the way everything went down. But for me, to watch him stand up there and handle everything the way he did, that was pretty cool. I thought he did a great job.”

No doubt, Kiffin comes with a huge warning tag. He’s young and petulant, prone to sticking his foot in his mouth and ticking people off with his bluster and bravado.

He’s shown he hasn’t mastered the NCAA rulebook yet, especially when it comes to important details like talking or tweeting about kids who have committed, but not yet signed their scholarships.

But while these issues create doubt and skepticism among the media and fans, it doesn’t much matter as long as the USC players who joined Barkley to watch Wednesday’s news conference are behind Kiffin.

Especially Barkley, the unquestioned leader of the team.

It’s been nearly a week since reports first surfaced that Carroll was leaving USC for the Seattle Seahawks, and it was Barkley who held the team together, urging teammates and recruits to stick with the program.

And Wednesday, he said he had Kiffin’s back.

“We’re ready to get after it, we’re fired up,” Barkley said. “This is a great hire for us, a perfect fit.”

Kiffin makes for great commentary for jilting Tennessee after just one season, but as long as his players and the staff are on board with him at USC, does it really matter what anyone else thinks?

He seemed every bit the 34-year-old he is Wednesday, not very commanding and a bit underwhelming as he addressed the media.

But his job is to run a clean program, recruit and develop players and get them to perform at a high level Saturdays.

He may not own a news conference with his charisma, but as long as he wins and stays out of trouble, it won’t matter.

“You know where he has a presence?” asked Orgeron. “With the players. I really wish you could see the way the (Tennessee) players acted when he was with them. In the team meetings, and the way they responded to him. I really believe he’s the perfect man for the job.”

Orgeron was on Carroll’s first staff in 2001 when Kiffin was a young assistant, and it didn’t take long for Kiffin to make an impression.

“I remember the first day he came here, we were in a recruiting meeting, and he’s got all the answers. And I’m looking at Pete going, `Who is this guy?’ But you know what, most of the time he was right.”

Time will tell if Kiffin is the right hire. But Wednesday, the most important voice in the room vowed commitment to him.

As far as good starts go, having Barkley’s support is about as good as it gets.

Vincent Bonsignore is an NFL columnist for the Southern California News Group. Having covered the Los Angeles sports scene for more than two decades, Bonsignore has emerged as one of the leading voices on the Los Angeles Rams and Los Angeles Chargers, the NFL and NFL relocation.